Y.I. Kolchugin, M.Y. Spodobaev

This article is about protected HF-band antenna-feeder instant readiness devices based on underground antenna arrays developed in branch of NIIR - SONIIR. Short analysis of modern tendencies in protected HF-band underground antenna array technologies is held, mentioning the use of elliptically polarized electromagnetic waves, use of interface and phasing devices (including automatically adjustable ones), creation of emitting structures as underground antenna arrays. It is mentioned that a number of devices developed in branch of NIIR - SONIIR meet those tendencies and could be considered as new generation of HF-band underground antennas. Example of protected antenna-feeder device (AFD) based on underground antenna array is discussed. Composition and structure scheme is listed, main ideas are discussed. Emitter description is given it is a turnstile antenna made up from two perpendicular horizontal triangle wire vibrators placed inside solid dielectric cover. The description of antenna-feeder devices: interface and phasing devices, travelling wave indicator is given. Scheme of interface device is symmetric contour that looks similar to low pass filter (LPF). Scheme of phasing device is two cascade symmetric contour similar to LPF. Phasing device is capable of altering its electric size within 180° which allows changing polarization without further commutation. Results of theoretical and experimental studies of underground antenna array sample are listed. Numerical experiments resulted in: radiation pattern (RP), directivity as function of frequency, axial ratio, gain. Besides numerical experiments were used to study echo suppression which increase interface device capabilities. Experiments were used to find out natural vibrator conditioning and control characteristics of interface devices. Antenna was also used to set up a radio connection between different respondents. Experiments showed that antenna provides reasonable channel quality up to 600 km in the direction with maximum directivity and up to 200 km in arbitrary direction.